This invention relates to an optical fiber connector and to a ferrule for use in such a connector. In particular, the invention relates to a fiber optic connector having an improved ferrule structure that supports and positions the optical fiber in the connector for communication with a second fiber.
The invention also provides a new ferrule structure, for a fiber optic connector, having advantages in manufacture ease and cost.
Fiber optic communication cables typically include at least one light transmitting optical fiber clad in an optically insulating material. The cladding protects the glass fiber, and prevents dispersion of light out of the optical fiber The fiber optic cable usually has a protective external buffer, typically of a plastic material, which may or may not be removed to terminate the cable.
The growing use of fiber optic systems creates a need for a connector capable of coupling segments of light-conductive cable for maximal light transmission. To achieve efficient light transfer between fiber optic cables, the optical fibers must be aligned to high precision, as well as properly spaced with or without touching, whichever is specified. The alignment and spacing requirements are exceedingly demanding, due to the minute, micron-size diameter of the optical fibers being connected, coupled or otherwise terminated.
A known fiber optic connector has a ferrule that holds the final length of the fiber in place so that it can abut another fiber at a faceted end. Each such connector ferrule is to have a precision bore that receives and thereby positions a fiber, to achieve the proper alignment. Even minute movement or errors in fiber position can cause significant optical losses. These problems can be even more acute with non-adhesive connectors, i.e. connectors in which the fiber is secured mechanically rather than with epoxy or other adhesive. In at least one non-adhesive connector, a relatively long length of the fiber, with the buffer layer removed, is to be supported and positioned. If a ferrule having a large diameter bore terminating in a small opening is used to hold the fiber, the ferrule can contain a substantial length of unsupported, unbuffered fiber. This long unsupported fiber is subject to flex, which can cause excessive detrimental optical loss and even fiber breakage. Unwanted flexing of the fiber is particularly apt to occur during the polishing of the facet end of the optical fiber.
U.S. Pat. Nos 5,088,804 and 4,679,895 disclose fiber optic connectors that secure an optical fiber mechanically, and without adhesives.
It is known to support the unbuffered fiber in a connector within a ceramic ferrule having a small and highly concentric bore through its total length. The precision bore extends to the facet end of the connector. The ceramic ferrule supports the fiber over much of its unbuffered length and hence aligns and positions it. However, such ceramic ferrules with relatively long precision bores are costly. They are used because small bores or channels of comparable length and of the accuracy needed cannot easily be made in non-ceramic materials with present technology. A major problem is that drilling or otherwise manufacturing a ferrule requires a through hole of small diameter and precise concentricity, typically in the order of 0.005 inch diameter and 0.5 inch length. Present manufacturing methods encounter significant problems in forming precision holes whose length is more than ten times their diameter. This problem has led to the use of the foregoing costly ceramic ferrules, or to adhesives in the connector.
Accordingly, an object of this invention is to provide a structure for a fiber optic connector that supports a length of unbuffered optical fiber with dimensional precision, and with relatively low cost and readily fabricated connector parts.
It is also an object of the invention to provide a method of making a relatively low cost connector ferrule which can support an unbuffered optical fiber with the proper concentricity and alignment for the fiber.
Another object of the invention is to provide a ferrule useful with non-adhesive optical fiber connectors and characterized by relatively precise dimensions and low cost.
A further object of the invention is to provide a ferrule which can be made of less expensive materials than ceramic ferrules and yet provides the proper fiber alignment for use in high quality optical fiber connectors.
These and other objects and features of the invention will be apparent from the following description and the drawing.